How many digits should be reported in forensic breath alcohol measurements?

Uncertainty is an inherent property of all measurements. The magnitude of this uncertainty will determine the number of meaningful digits that should be reported in a measurement result. Several statistical arguments are considered providing evidence that three digit truncated results are more appropriate than two since the first significant digit of the combined uncertainty (standard deviation) in breath alcohol measurement is found in the third decimal place.

The accuracy of handheld pre-arrest breath test instruments as a predictor of the evidential breath alcohol test results.

Drunk driving is a serious threat to public safety. All available and appropriate tools for curbing this threat should be employed to their full extent. The handheld pre-arrest breath test instrument (PBT) is one tool for identifying the alcohol-impaired driver and enforcing drunk driving legislation.

Estimating the measurement uncertainty in forensic blood alcohol analysis.

For many reasons, forensic toxicologists are being asked to determine and report their measurement uncertainty in blood alcohol analysis. While understood conceptually, the elements and computations involved in determining measurement uncertainty are generally foreign to most forensic toxicologists. Several established and well-documented methods are available to determine and report the uncertainty in blood alcohol measurement.

Differentiating new cannabis use from residual urinary cannabinoid excretion in chronic, daily cannabis users.

Aims: To develop and validate empirically a mathematical model for identifying new cannabis use in chronic, daily cannabis smokers.

Design: Models were based on urinary creatinine-normalized (CN) cannabinoid excretion in chronic cannabis smokers.

Setting: For model development, participants resided on a secure research unit for 30 days.

Employing components-of-variance to evaluate forensic breath test instruments.

The evaluation of breath alcohol instruments for forensic suitability generally includes the assessment of accuracy, precision, linearity, blood/breath comparisons, etc. Although relevant and important, these methods fail to evaluate other important analytical and biological components related to measurement variability. An experimental design comparing different instruments measuring replicate breath samples from several subjects is presented here.

Estimating the uncertainty associated with Widmark's equation as commonly applied in forensic toxicology.

No computation is performed more frequently by forensic toxicologists than that involving Widmark's equation. The equation is employed to estimate either the number of drinks consumed or the corresponding blood or breath alcohol concentration. Despite the wide use of Widmark's equation, rarely is an uncertainty estimate also provided.

Results of a proposed breath alcohol proficiency test program.

Although proficiency test programs have long been used in both clinical and forensic laboratories, they have not found uniform application in forensic breath alcohol programs. An initial effort to develop a proficiency test program appropriate to forensic breath alcohol analysis is described herein. A total of 11 jurisdictions participated in which 27 modern instruments were evaluated.

Factors associated with breath test refusals in drunken driving arrests.

Objective: Jurisdictions with per se breath alcohol legislation rely heavily on breath test evidence in prosecuting drunk driving cases. Depending on other legal considerations, where subjects refuse the breath test, prosecution may be more difficult. The objective was to identify factors significantly associated with the risk of test refusal.

Breath alcohol measurement variability associated with different instrumentation and protocols.

Breath alcohol measurement has variability resulting from instrumental, procedural and biological components. Reliable estimates of the standard deviation (S.D.